1. Field of the Invention
This invention relates to a receiving apparatus preferably used in telephone with functions to process a caller-identification, and more particularly to a function, which is able to process the caller-identification and automatically detect signal of channel seizure and then process the message-waiting.
2. Description of Related Art
The emergence of the telephone has allowed two far apart places to be brought seemingly close together. Nowadays, due to the highly developed technology of telecommunication, functions of the telephone have been significantly promoted either, for example, functions of a fixed forward, a call waiting, a caller-identification, and a voice mail box. The function of a caller-identification apparatus is such that when a call rings, the receiver is able to obtain the telephone number and other related information through the caller-identification to decide whether to receive the call or not and thus prevent receiving unnecessary calls. The function of a voice mailbox is to provide a service for leaving messages when the receiving party can't receive the call at the time it was placed.
The protocol of sending a caller-identification (caller-ID) was developed by Bell Communications Research (Bellcore). When a call is dialed, the data message of the caller-ID is sent from the switchboard to the destination every two seconds. Referring to FIG. 1, the protocol for sending a caller-ID is arranged in a time sequence, in which a ring 10 is sent first. About 0.5 seconds later a signal of a channel seizure 11 is sent and then, a mark 12 with 150 ms duration is sent. Finally the data message 13 including the data message of the caller-ID is sent. The next ring 14 is sent a few seconds later for the next cycle. The caller-ID is sent by utilizing a modularizing method of frequency shift keying (FSK) in which, for example, a frequency of 1200 Hz represents the logic state "1" and a frequency of 2200 Hz represents the logic state "0" and the sending rate is 1200 bits per second (bps). The signal of the channel seizure 11 is formed in a series of logic data mixed with a number of "0" and "1". Following that, a signal of mark 12 is in a form of continuous logic state "1". The first logic state "0" after the mark is interpreted as an end of the mark. Then the date, time and telephone number grouped as the information of the data message 13 are sent immediately after the mark 12.
If the caller ID user also has voice mail and a call is received while in an on-hook state, the switchboard will send a message-waiting. The protocol for sending a message-waiting is arranged in a time sequence as illustrated in FIG. 2. Referring to FIG. 2, the protocol starts with a channel seizure 21 having a duration of 250 ms, then a mark 22 and the data message 23 including the information of the message-waiting follows the channel seizure 21 sequentially.
In general, for a telephone having ability to process the caller-ID in an on-hook state, to save the power consumption, only the necessary parts of circuits are kept in a working mode such as the ring and the detecting circuits. Other parts of circuits are kept in a sleeping state. When the detecting circuits detect a ring, the circuits should activate all other related parts to process the caller-ID.
In the case that the user has applied the service of the voice mail box, since the message-waiting has no ring acting as the leading signal, the related parts to process the message-waiting need to be activated periodically to detect whether the signal of a channel seizure appears or not. If the signal of a channel seizure has been detected the circuit is kept in the working mode to process the incoming information.
The conventional method to process the caller-ID and the message-waiting utilizes a micro-controller to control the whole system, in which the micro-controller is always kept in working mode so that the micro-controller can sense the arrival of a ring and activate the related parts to process the caller-ID.
For the case to process the message-waiting, because there is no ring as the leading signal, the micro-controller has to activate the related parts for processing the message-waiting periodically to see if there is a signal of a channel seizure existing or not to decide if the related actions should be activated or not. This procedure can save the power consumption.
However the conventional receiving apparatus to process the caller-ID as described above has some problems as follows:
1. The micro-controller has to be always kept in the working mode to activate the related parts of circuits to detect a signal of a channel seizure. This causes the consumption of power and therefore causes the duration of use of the telephone to be reduced if the telephone is powered by battery. PA1 2. Some specially designed software is needed to accommodate the micro-controller for being able to detect the ring and the channel seizure. This increases the complexity. PA1 1. Without the need of an additional micro-controller as used in the conventional apparatus for detecting the ring and periodically waking up the related parts, most of parts of the caller-ID receiving apparatus in the invention can stay in the sleeping state when there is no signal in order to save the consumption of power. Therefore the available duration time of a telephone powered by battery is prolonged. PA1 2. All the control parts can be fabricated together in one single hardware circuit. Therefore without the need of a separate micro-controller and the software to support the micro-controller for detecting the ring and the signal of the channel seizure, the receiving apparatus in the invention can automatically detect the signal of channel seizure and process the data message of the message-waiting and the complexity can be reduced.